1. Field of the Invention
The present invention relates to a position control system for an unmanned automated vehicle (hereinafter referred to simply as "moving vehicle"), and more particularly to a position control system for a moving automobile, a moving mobile carrying device in a factory, or a moving vehicle for use in agriculture, civil engineering machinery and the like.
2. Description of the Prior Art
Heretofore, as a system for detecting the present position of a moving vehicle as described above, there has been provided a self-position detecting system constructed in such manner that an electric wave transmitted from transmitting sources located at a plurality of places is received by a receiver mounted on the moving vehicle, and the position of the moving vehicle is calculated by means of a direction or an azimuth of reception of the electric wave.
In such a self-position detecting system as described above, a plurality of transmitters for generating electric waves are required, so that there is the disadvantage that the whole system becomes expensive.
As a countermeasure, a system is described in, for example, Japanese Patent Laid-open No. 674766/1984 for detecting a self-position of a moving body by scanning a light beam emitted from the moving body in the circumferential direction centering around the moving body. In this system, light-reflecting means for reflecting the light beam in precisely the same direction as the incident light are secured at at least three positions apart from the moving body, and the moving body is provided with a beam source means, a light beam scanning means for scanning light beam emitted from the beam source means, and a beam receiving means for receiving light reflected from the light-reflecting means.
In the above system, differential azimuths between adjoining two light-reflecting means centering around the moving body are detected on the basis of received light output of the beam-receiving means, whereby a self-position of the moving body is calculated based on the detected angles and positional information of the light-reflecting means which have been previously set.
In the above described arrangement, however, positional information of the light-reflecting means must have been previously set, and the whole system is significantly affected adversely by even a slight error in the preset positional information of the light-reflecting means. Hence, for example, in agricultural work and the like, it becomes necessary for such operations that the positions of and positional information of the light-reflecting means, i.e., distances between two of the light-reflecting means and the differential azimuths between three light-reflecting means, must be previously set accurately prior to the work every time there is a change in the field working area, and the positional information obtained during these presetting operation must be input to the control means of the system. Accordingly, accurate measurement of the distances and relative angles of the light-reflecting means disposed in a wide working area, as well as the inputting operation therefor, are extremely complicated operations.